Flash lamp bulb



y 7, 1957 M. B. SKAGGS 2,791,112

' FLASH LAMP-BULB Filed June 10, 1953 lnv'en lrov Meri t B. Skaggs His A t tovneg.

FLASH LAMP BULB Merit B. Skaggs, Willoughby, Ohio, assignor to General Electric Company, a corporation of New York Application June 10, 1953, Serial No. 360,750

2 Claims. ((11. 67-31) The present invention relates to flash lamps of the type comprising a sealed glass bulb and combustible material 2,791,112 Patented May 7, 1957 ice 2 powders and potassium perchlorate powder bounded together by a suitable binder, such as nitrocellulose.

The bulb also contains a charge of combustion supporting gas, such as oxygen, at a pressure corresponding substantially to atmospheric.

On flashing of the lamp, the gas expands rapidly due to the intense heat of combustion and exerts a considerable and sudden force on the bulb 1. The bulb is usually coated on its inner and outer surfaces with a transparent lacquer to strengthen it. I

Flash lamps of the type described and claimed in the Pipkin patent referred to above and provided with ellipswithin the bulb to produce when ignited a flash of light ignition of the lamp. In U. S. Patent 2,306,563, patented December 29, 1942, by Marvin Pipkin, and assigned to the .assignee of the present application, a flash lamp having .a bulb of ellipsoidal shape is disclosed and claimed. Such lamps have been available commercially in small sizes, made possible by the strong ellipsoidal-shaped bulb. These lamps have enjoyed marked commercial success as .a result of their small size and high total light output.

The principal object of the present invention is to decrease the size and increase the strength of lamps of the above type. Further objects and advantages of the invention will appear from the following detailed description of a species thereof and from the appended claims.

In the accompanying drawing an embodiment of the invention is shown in which Fig. 1 is an elevational view of a flash lamp embodying the invention, and

Fig. 2 is a longitudinal sectional view on an enlarged scale of a blown and molded glass bulb embodying the invention and suitable for use in the lamp shown in Fig. 1.

Referring to the drawing, the flash lamp comprises a hermetically sealed blown and molded glass bulb I having a metal base 2 of the bayonet type secured as by a ring of cement to the tubular neck 3 of the bulb with its rim abutting against the curved part of the bulb. While the invention is also useful in conjunction with flash lamps of the type wherein the sole source of light is constituted by a compact body of agglutinated material within the bulb and comprising a combustible and a supporter of combustion, such as the lamp disclosed and claimed in U. S. Patent No. 2,291,983, Pipkin, issued August 4, 1942, and assigned to the assignee of this application, it is illustrated in the drawing as embodied in the type of flash lamp wherein the bulb contains combustible material 4 in the form of shredded aluminum foil of the type disclosed in U. S. Patent No. 2,351,290, Ripple and Isaac, issued June 13, 1944, and assigned to the assignee of this application.

An igniter for the combustible material is made up of a short, fine tungsten filament 5, mounted on the inner spaced ends of the current inleads 6 and 7, and a coating 8 of fulminating material on the filament and in the form of beads on the ends of the inleads 6 and 7. The inleads are sealed into the stem 9 of the bulb and are connected to the usual contacts of the bayonet base 2. The fulminating material is preferably of the type disclosed in United States Patent No. 2,280,598, George H. Merideth, issued April 21, 1942, and assigned to the assignee of this application. The fulminating material therein disclosed comprises a mixture of magnesium and zirconium metal oidal bulbs having a maximum diameter of about 1% inches have proven-eminently satisfactory for photographic purposes and the hazard of shattered bulbs has been practically eliminated in such lamps.

However, an increased safety factor is a highly desirable feature in photo flash lamps,- and in accordance with the present invention the strength of such flash lamp bulbs against explosive forces is further and markedly increased to provide a higher factor of safety for such lamps than has been attained heretofore, together with a decrease in the maximum diameter of the lamp bulb to provide greater convenience in handling, packaging, and the like.

These advantages are obtained in the bulb 1 of the draw-ing which combines four different contours in contiguous zones 10, 11, 12 and 13 (Fig. 2), each having a projected length in a determined ratio to the over-all length of the body portion of the bulb containing the combustible material 4.

As shown in Fig. 2 of the drawing, the body portion of the new bulb 1 has an end zone 10, the center of curvature 14 of which coincides with the longitudinal axis A-B of the bulb. The zone 11 contiguous with the zone 10 has a center of curvature 15 offset from the said longitudinal axis, but lying Within the bulb and located on the projection of the common boundary between the zones 11 and 12. The succeeding zone 12 is tubular in shape and the zone 13 at the base end of the bulb has a center of curvature 16 located outside the bulb and on the projected common boundary between the contiguous zones 12 and 13.

In actual bulbs blown and molded in accordance with the invention, the over-all length C of the body portion was 1.625 inches; the projected length of zone 10 was .454 inch; that of zone 11 was .161 inch; the length of zone 12 was .300 inch, and the projected length of zone 13 was .710 inch. The radius of zone 10 was .454 inch; that of zone 11 was .761 inch, and that of zone 13 was 1.290 inches. The diameter of zone 12 was 1.0 inch which, of course, was the maximum diameter D of said body portion. All dimensions given are outside dimenslons.

The projected area of the body portion of these bulbs was 4.8 square inches and the volume thereof approxiof the maximum diameter D of the said body portion to the radius of Zone 10 is approximately 2.2; to the radius of zone 11, approximately 1.31; to the diameter of zone 12, approximately 1.0, and to the radius of zone 13, approximately l/ 1.29.

The average thickness of the glass wall at the part of maximum diameter, that is zone 12, of the actual bulbs was .015 inch to .017 inch in minimum thickness. The

minimum wall thickness of the corresponding part of the prior ellipsoidal bulbs averages .012 to .013 inch.

Of course the part of maximum diameter of both types of blown bulbs has the minimum wall thickness and is, therefore, the weakest portion of the bulb, other factors being equal. It will be noted from the figures given above that the wall thickness of the new bulb is thus of the order of 25 percent greater at the part of maximum diameter which results in a substantial increase in the strength of the bulb and a greater safety factor against shattering.

A further feature of the new bulb resulting in increased strength .is the substantial reduction in the degree of curvature of the zone 13 of the bulb of the present invention as compared to the degree of curvature of the corresponding part of an ellipsoidal bulb which is approximately the same as that of zone 10. This lessening of the degree of curvature of zone 13 of the bulb also results in a greater wall thickness and a more uniform wall thickness throughout this portion which last is highly advantageous in removing strains in the glass during annealing of the bulb.

Further, in lacquering the inner and outer surfaces of the bulb, it has been demonstrated that a more even coating of strengthening. lacquer can be applied to the gently curving surfaces of the zone 13 by either the conventional dipping or spraying methods presently used than it is possible to obtain by such methods on the corresponding part of ellipsoidal bulbs.

The above-described combined features of the bulb of the present invention result in a substantial increase in the strength of the bulb against explosive forces bult up therein when the lamp is flashed. The safety factor of bulbs embodying the invention is thus even greater than that of the ellipsoidal bulbs of the Pipkin patent mentioned above, to the end that the hazard of shattered bulbs is lessened.

The remainder of the bulb, that is the neck portion 3 and the so-called cullet portion 17, is conventional except that the neck portion, which has an outer diameter of .540 inch and an over-all length of .500 inch, is joined to the zone 13 of the bulb by a short outwardly curved rim .18 on the neck portion. The rim 18 has a radius of .103 inch and a center of curvature 19 located outside the bulb and spaced a distance of .057 inch from the outer boundary of zone 13. The rim of the base 2 abuts against the curved rim 18 of the neck in the completed lamp.

The cullet 17 is .750 inch long and flares outwardly to a maximum diameter of .770 inch from the :neck 3.

The fabrication of a lamp incorporating the new bulb is accomplished in the usual manner. The cullet portion 17 is first removed and the inside of the neck Sand the body portion of the bulb is then lacquered. The stem 9 with the inleads ,6 and 7, the filament 5, and the coating 8 of fulminating material mounted thereon is fusion sealed into the neck 3.01? the bulb 1 after the combustible material 5 has been placed in the body portion of the bulb 1. After the usual stretching of the seal to remove strains from the glass, oxygen at a suitable pressure is introduced into the bulb through the exhaust tube (:not shown) which is then sealed. The 'base 2 is thereafter cemented to the neck 3 with the inleads 6 and 7 connected to the base contacts, and the outer coating of lacquer is applied to the bulb to complete the lamp.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A flash lampcomprising a blown and molded sealed glass bulb containing a charge of combustible flash material, the body portion of said bulb enclosing the said material having four contiguous zones of different contour extending different projected distances along its lon gitudinal axis, the first of said zones having a center of curvature on said longitudinal axis and on the common boundary between said zone and the succeeding zone, the ratio of the total length of said body portion to the pro jected length of said first zone being approximately 3.58 and the ratio of the maximum diameter of said body portion to the radius of said first zone being approximately 2.20, the second of said zones having a center of curvature offset from said longitudinal axis but within the bulb and located on the projection of the common boundary between said second zone and the succeeding zone, the ratio of the total length of said body portion to the projected length of said second zone being approximately 10.09 and the ratio of the maximum diameter of said body portion to the radius of said second zone being approximately 1.31, the third of said zones being tubular, having a diameter of approximately equal to the maximum diameter of the said body portion and a length such that the ratio of the total length of said body portion to the length of said tubular zone is approximately 5.41, and the fourth of said zones having a center of curvature outside said bulb and on the projection of the common boundary between said third and fourth zones, the ratio of the total length of said body portion to the projected length of said fourth zone being approximately 2.29 and the ratio of the maximum diameter of said body portion to the radius of said fourth zone being approximately 1/1.29, whereby said body portion has a substantially uniform wall thickness throughout its length and provides gradually curving-surfaces for the application gfluniform coatings of bulb strengthening lacquer to the u b.

2. A flash lamp comprising a blown and molded sealed glass bulb containing .a charge of combustible flash material, the body portion of said bulb enclosing said material having four contiguous zones of different contour, the first of said zones having a center of curvature on the said longitudinal axis and on the common boundary between said zone and the succeeding zone, the projected length of said first zone being approximately .454 inch and the radius thereof being .454 inch, the second of said zones having a center of curvature offset from said longitudinal axis but within the bulb and located on the projection of the common boundary between said second zone and the succeeding zone, the projected length of said second zone being .161 inch and the radius thereof .761 inch, the third of said zones being tubular, having a diameter of approximately 1 inch and a length of approximately .300 inch, and the fourth of said zones haw ing a center of curvature outside said bulb and on the projection of the common boundary between said third and fourth zones, a projected length of .710 inch and a radius of 1.290 inches, whereby said body portion has a substantially uniform wall thickness throughout its length and provides gradually curving surfaces for the application of uniform coatings of bulb strengthening lacquer to the bulb.

References ,Cited'in the file of this patent UNITED STATES PATENTS 2,264,043 Ledig Nov. 25, 1941 2,270,162 De Margitta Jan. 13, 1942 2,306,563 Pipkin Dec. 29, 1942 

